1. Field of the Invention
The present invention relates generally to the area of x-ray imaging systems and devices used with such diagnostic x-ray systems. More specifically, the present invention relates to a C-arm x-ray imaging apparatus that incorporates new and improved mechanisms for adjustment and control of the C-arm during usage.
2. Background of the Invention
It is frequently desired to conduct an x-ray examination of a patient by positioning the x-ray equipment such that a number of different views of the area of interest, and from several different positions, may be obtained. It is also preferable to do so without the need to reposition the patient. Mobile C-arm x-ray diagnostic equipment, such as that shown in FIGS. 4A and 4B of the present application, has been developed to meet these needs and is now well known in the medical and surgical arts. The C-arm x-ray machine is especially useful in that it is small enough and mobile enough to be present in an operating or exam situation without requiring the physician to repeatedly move or requiring the patient to change positions to obtain suitable radiographic images.
C-arm imaging systems are widely used in the medical arts. Examples of their uses include bone density measurement and fluoroscopic imaging during surgical procedures. The term xe2x80x9cC-armxe2x80x9d refers to the generally C-shaped member that has an x-ray source and an image receptor, or detector, mounted on opposing ends of the C-arm. In this fashion, x-rays emitted by the source are incident on and detected by the detector. The x-ray source and the detector are positioned such that when, for example, a human extremity is interposed between the x-ray source and the image receptor, thereby exposing the extremity to x-ray radiation, the receptor produces data representative of characteristics of the interposed extremity. The data produced may be displayed on a monitor and electronically saved.
The C-arm portion of the machine is normally mounted such that it is permitted two degrees of freedom. First, the C-arm track is slidably mounted to a C-arm support member so as to be movable in relation to the support member. This permits the x-ray source and image receptor to be moved rotatably about the are of curvature of the track in the C-arm. Second, the C-arm support member permits rotation of the C-arm about its axis. Often the support member is in the general shape of an L and may be referred to as the yoke. Mobile C-arms have a third degree of freedom in that they are free to move in a plane that is horizontally parallel to the floor and a fourth in that the C-arm can be raised and lowered.
Obviously, a support structure that permits rotation and movement of such a C-arm must be constructed to withstand very large torsional, tensile and compressive stresses and moments. It must also be constructed so as to provide a support structure that is heavy enough and a center of gravity that is low enough to avoid imbalance and tipping of the machine when the C-arm and Yoke are rotated or raised, which in some cases causes a dramatic shift in the center of mass of the equipment.
Additionally, C-arm x-ray equipment must be delicately positioned in order to render the image or images desired by the physician. Unfortunately, the weight of the support structure makes it difficult to position the C-arm. Therefore, it is desirable to design a source of frictional drag between the C-arm and the support member as well as on the C-arm track to assist with this positioning.
It is also desirable to balance the C-arm, x-ray source, x-ray detector and Yoke so that relatively little physical effort is required to move the C-arm about the orbital rotation axis and the lateral rotation axis. One manner of accomplishing this is to design the C-arm such that its center of mass is as close as possible to the orbital and lateral rotation axes.
Some C-arm designs require a center of mass that is separate and apart from the axis of rotation. In these unbalanced designs, the user must exert significant force to rotate the apparatus. This physical exertion generally detracts from other, more significant tasks a health care provider may be undertaking. Also, unbalanced designs can be dangerous to both the operator and the patient. For example, unbalanced C-arms require much more powerful braking systems. Without a braking system, the C-arm could rotate downwardly and forceably strike a patient during positioning or during examination. Unfortunately, a completely balanced C-arm x-ray imaging system is nearly impossible to design due to variances in manufacturing.
It is therefore an object of the present invention to provide a C-arm x-ray apparatus that is either optimally balanced or that requires little effort to rotate. It is yet another object of the present invention to provide such a device that requires relatively few parts and that can be easily manufactured. It is also an object of the present invention is to increase the friction between the C-arm and the Yoke so as to improve rotational control of the C-arm when the brake is not applied. Yet another object of this invention is to provide such a device while not increasing the overall length of the C-arm machine, which increase in length would also serve to decrease overall stability of the machine. It is yet another object of the present invention to provide an aesthetically pleasing and aseptic device.
The present invention has obtained these objects. It employs a device to control the rotation of the C-arm when the physician or health care provider is adjusting the C-arm machine to ready it for examination purposes. Additional objects and advantages of the invention will be set forth in the description that follows. Other objects and advantages may be learned by practice of the invention.